1. Field of the Invention
The present invention relates generally to maritime operations, and more particularly to systems for moving cargo containers.
2. Related Art
In the past, maritime cargo operations consisted of moving numerous small items like boxes, drums, and crated goods, using cranes and physical labor to load and off-load these from the transport ships. Although dockside transport was more efficient, it was still common to move goods to or from undeveloped shorelines. With the increased volume of international trade, much more efficient means of moving goods arose within the maritime shipping industry. Today, the vast majority of maritime cargo is moved via intermodal containers, allowing for huge volumes to be efficiently moved between key ports. As a result, most of today's shipping is configured for carrying and utilizing commercial cargo containers.
Commercial cargo containers are, for the most part, manufactured according to specifications set by the International Organization for Standardization (known as the “ISO”). These specifications include standards for strength, water-tightness, mobility, and security. Their size is typically forty feet long, eight feet wide and eight feet, six inches high (i.e., 40′×8′×8′6″), and can weigh over thirty-four tons fully loaded with a capacity of over 2,720 cubic feet. Other ISO standard containers can measure 20′×8′×8′6″, 45′×8′×8′6″ or 45′×8′×9′6″. When referring to commercial containers, we mean these or similarly strong and large (4′ or more) containers for cargo, regardless of use for commercial, non-profit or governmental purposes.
Today's deep draft, large cargo vessels, which are configured for carrying and utilizing ISO standard cargo containers and the like, cannot approach shallow shores or even ports. They must use modern port facilities with special cargo handling equipment (e.g., cranes, etc.) or must be off-loaded outside the surf zone and their containers transferred to the beach via smaller craft. The latter method is highly inefficient because it requires delicate alignment of the containers while transferring containers between dynamic, floating platforms with the transfer crane introducing additional motion. Also, the smaller craft must return from the beach empty to pick up another load, greatly reducing their productivity.
Several systems exist which may deliver cargo containers either through or over the surf zone. The most commonly used method is lighterage which uses a small boat that is large enough to hold one or more commercial containers in its well deck. The smaller boat pulls along side the container ship and a container is placed aboard it using a crane. The smaller boat is then driven to the beach by its crew. This type of boat has a shallow draft that allows it to approach the beach and a ramp that is dropped onto the beach to allow the cargo container to be transferred to the beach. The emptied small boat must then return to the container ship to repeat the cycle. This solution, however, also suffers from a low transfer rate due to required return trips to the large ship while empty. This is further impacted by the required distance the large ship must remain off shore.
Greater transfer rates are possible from ships from which the containers on wheels may be driven off. These ships are called roll-on, roll-off (RO-RO) ships. Their use at a primitive beach or shore facility, however, requires a beach with an atypically steep slope that allows the deep container ship to approach the shore or the construction of a pier.
Thus, while today's intermodal container system is a huge benefit to all and critical to international trade, it also gives rise to the drawbacks highlighted above. Because of the expense of a high-volume dockside container facility, these tend to cater to specialized ships. These ships in turn only operate efficiently—sometimes only—at the larger ports, which have the high-volume facilities. If goods being transported by containers are destined for small ports or unimproved shoreline, they must be transported by land or broken up and re-loaded as break-bulk goods for local operations. Further, because of the volume of shipment by intermodal containers, there are fewer vessels in service equipped for break-bulk or lighterage transport, and the time and expense for secondary transport (after container transport to a large port) is increasingly prohibitive. Moreover, in some applications where it is still highly desirable to use container shipment to primitive locations (e.g., military logistics), significant expense and time is needed to set up temporary off-loading facilities. This is far from ideal, because it is too expensive for commercial operations, but still slow and vulnerable to attack. With respect to amphibious lighters, these are difficult to load in an open sea. The relative motion of the rolling container ship, the container's swinging on the crane bridle, and the lighter's bobbing on the waves make insertion of a container into the lighter a slow operation. RO-RO ships used on an average beach require construction of a temporary causeway that allows the containership's ramp to discharge its containers to it while the ship stays in water deep enough for its draft. This process, however, adds to the time required before cargo is transferred and increases the costs involved.
Given the advantages and dependence on maritime container shipping, but the disadvantages noted above, what is needed is an improved apparatus, system and method for moving maritime cargo containers to locations that are not equipped with a high-volume container facility.